1. Field of the Invention
The present invention relates to a semiconductor device used for control of a large current for example.
2. Background Art
Japanese Patent Laid-Open No. 2013-152996 discloses a semiconductor device having an IGBT and a diode formed on a substrate. This semiconductor device is generally called a reverse conducting insulated gate bipolar transistor (RC-IGBT).
In some cases, a trench gate is formed in each of an IGBT and a diode in an RC-IGBT. The trench gate in the diode is provided for the purpose of increasing the withstand voltage with respect to the Vce voltage (emitter-collector voltage). The gate capacitance can be reduced by electrically insulating the trench gate in the diode from the trench gate in the IGBT. There is a problem that in such a structure the depletion layer cannot extend smoothly in the substrate depth direction between the trench gate in the IGBT and the trench gate in the diode and a sufficiently high withstand voltage cannot be secured.